The present invention concerns methods and compositions for inhibiting or blocking fertility in a male mammal by the administration of a retinoid or retinoid derivative that is able to act as an antagonist or inverse agonist of a retinoic acid receptor (RAR). The effect is reversible upon cessation of treatment with the RAR antagonist or inverse agonist.
The prevention of unplanned pregnancy in humans and other mammals is of continuing concern for both the developing and the developed world. A variety of methods and products have been proposed or developed for the prevention of pregnancy; these products include: surgical sterilization, condoms, birth control pills containing progestin or a combination of progestin and estrogen, subdermal implants containing delayed release forms of progesterone, intrauterine devices, spermicidal creams or gels, and intravaginal barriers such as sponges or diaphragms.
These various methods each have certain advantages and certain drawbacks. The most common non-surgical birth control method in the United States is the birth control pill (xe2x80x9cthe Pillxe2x80x9d), which contains synthetic progestin and estrogen; synthetic hormones similar to those produced naturally in a woman""s body. The Pill works primarily by suppressing the release of eggs from a woman""s ovaries.
Within two years after its introduction in 1960, approximately 1.2 million women were using oral birth control, and by 1973, about 10 million women were using the Pill. However, in recent years questions have arisen about the health risks involved in continued long term use of contraceptive hormones. There have been reports of increased risk of certain forms of cancer, such as breast and cervical cancer, though the use of the Pill.
Surgical sterilization, whether through tubal ligation or vasectomy, is nearly 100% effective, but is only sometimes reversible. Reversal of surgical sterilization usually requires further surgery.
Condoms, made of either synthetic polymer materials or animal skin, are less effective n birth control pills and their effectiveness is further subject to subversion through the possibility that small breaks may be present, permitting leakage of semen. Additionally, the use of a condom requires the affirmative action of the male, usually immediately prior to the initiation of sexual intercourse and some men report a loss of sensation through the use of condoms. Hence, subject noncompliance is also an issue in the use of condoms.
Subdermal implants, such as the NORPLANT(copyright) implant device, are quite effective contraceptive means. The implant comprises a set of silicone rods that are inserted under the skin of the upper arm. The implant contains hormones, such as progestin, levonorgestrel and progesterone, that are slowly released over a period of time of up to five years. Side effects may be similar to those involved in the use of birth control pills, and include a risk of developing ovarian cysts. Additionally, while the implant can be removed, the procedure is difficult even for skilled surgeons due to the formation of scar tissue around the implant.
Intrauterine devices (IUDs) are small devices that are typically either made of copper or impregnated with progesterone. These must be inserted (and removed) by a doctor. Depending on the design, the devices appear to interfere with sperm motility or the implantation of the fertilized egg in the uterine wall. Side effects can include cramps, backache, spotting, or heavy periods, and women may have an increased risk of ectopic pregnancy or infertility. IUDs are usually not recommended for women who have not had children or who think they will have children in the future due to these latter risks. Normally, the contraceptive effects are reversible upon removal of the device.
Barriers such as diaphragms and sponges are usually used in conjunction with a spermicidal cream, foam, or gel. The effectiveness of such devices is between about 90% and about 95%. The user can insert them as long as a number of hours before sexual intercourse, and the effects are temporary; if pregnancy is subsequently desired, the woman can discontinue their use with a concomitant return of fertility.
With the exception of surgical sterilization and the use of condoms, all of the methods in common use affect female fertility with no effect on male fertility. As mentioned above, the former of these methods is irreversible and the latter is neither inherently as effective as other methods, nor is compliance as high. A male contraceptive that is not required to be applied immediately prior to intercourse would provide a contraceptive alternative to the traditional methods of contraception.
A number of compositions have been proposed for use as a male contraceptive. Thus, U.S. Pat. No. 5,501,855, to Talwar et al., describes application of neem (Azadirachta indica) oil by injection to the vas deferens in an amount effective to block the fertility of the male by spermatogenic arrest. A single injection was reported to be effective to block fertility over the 9 month period of observation reported in the ""855 patent.
U.S. Pat. No. 4,677,193 and International Patent Publication No. WO 94/19370, both to Rivier et al., describe a hypothalamic peptide hormone (termed GnRH) that functions to trigger the release of gonadotropic hormones such a luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the female. These references also mention that antagonists of GnRH are effective to arrest spermatogenesis in male mammals. This treatment apparently requires supplemental testosterone to be provided with the treatment in order to maintain libido.
U.S. Pat. No. 5,744,448, to Kelton et al., describes the cloning, expression, and purification of human FSH receptor, or mutants or fragments thereof that retain the ability to bind FSH. One possible use of the FSH receptor is described as a method for preventing spermatogenesis in a male patient.
U.S. Pat. No. 4,182,891, to Metcalf et al., and U.S. Pat. No. 4,134,918, to Bey et al. describe compounds said to be useful in inhibiting spermatogenesis. The ""891 patent describes acetylenic derivatives of amino acids, and the ""918 patent describes halomethyl derivatives of amines.
International Patent Publication No. WO 97/24901, to Bandman et al., describes the amino acid sequence of a polypeptide termed Lung Growth Factor Variant (LGFV), which is said to play a role in various physiological processes, including spermatogenesis.
U.S. Pat. No. 5,753,231, to Herr, et al., describes a female contraceptive vaccine prepared from antibodies raised to a recombinant primate acrosomal sperm antigen. The vaccine elicits an anti-sperm immune response, resulting in inhibition of fertilization. Also described are contraceptive compositions containing such an antibody in a carrier for vaginal application.
None of the references cited herein are admitted in any manner to be prior art against the present application.
The present invention concerns the discovery that certain agents that are able to block the binding of retinoic acid (RA) or other RAR ligands to RAR receptors, and thereby prevent activation of RARs, are also able to inhibit spermatogenesis in a male mammal.
It has been known for some time that among the various results of a severe vitamin A (retinol) deficiency in mammals is sterility and blindness. See Eskild, W. and Hansson V., Vitamin A Functions in the Reproductive Organs in Vitamin A in Health and Disease 531 (Blomhoff, R. ed., 1994) (hereinafter Eskild). A complete deficiency in retinoids is fatal. Administration of retinoic acid in the absence of retinol can alleviate many of the symptoms of vitamin A deficiency, giving rise to blind and sterile animals that remain otherwise healthy.
Researchers have also noted that treatment of vitamin A-deficient rats (in which there was a complete spermatogenic arrest) with vitamin A replacement results in restoration of normal spermatogenesis; reinitiation of spermatogenesis occurs in rats within 24-48 hours following vitamin A replacement. Huang, et al., 112 Endocrinology 1163-71 (1983), incorporated by reference herein.
A vast array of specific metabolic, developmental, and catabolic processes appear to be directly or indirectly regulated in vivo by comparatively small molecules such as steroids, retinoids and thyroid hormones. The mechanism whereby a single such compound can contribute to the regulation of numerous different cellular events was the subject of much speculation until relatively recently, when it was discovered that these compounds each share the ability to bind to transcriptionally active proteinaceous receptors. These protein receptors, in turn, are able to bind specific cis-acting nucleic acid regulatory sequence regions, termed response elements or RE""s, located upstream of the coding sequence of certain genes and to activate the transcription of these genes. Thus, these proteinaceous receptors can serve as specific, ligand-dependent regulators of gene transcription and expression.
The amino acid sequences of these various receptors were quickly found to share regions of homology, thus making each such receptor a member of a family of ligand-modulated receptor molecules. This family has been termed the steroid superfamily of nuclear hormone receptors; nuclear, because the receptors are usually found in high concentration in the nucleus of the cell, although it is not clear that these are always the only relevant locations in which these receptors are found, or that transcriptional activation is the only activity that the receptors possess.
Further study of the structural and functional relationship between the nuclear hormone receptors has shown certain characteristics in common between them in addition to sequence. homology. See e.g., Evans et al. Science 240:889-895 (1988). As stated above, the nuclear hormone receptors are able to bind to cis-acting regulatory elements present in the promoters of the target genes. The glucocorticoid, estrogen, androgen, progestin, and mineralcorticoid receptors have been found to bind as homodimers to specific response elements organized as inverted repeats.
Another class of nuclear hormone receptors, which includes the retinoid receptor RAR (retinoic acid receptor), the thyroid receptor, the vitamin D receptor, the peroxisome proliferator receptor, and the insect ecdysone receptor bind their response element as a heterodimer in conjunction with the retinoid X receptor (RXR), which in turn is positively activated by 9-cis retinoic acid. See Mangelsdorf, et al., The Retinoid Receptors in The Retinoids: Biology, Chemistry and Medicine Ch.8 (Sporn et al., eds. 2d ed., Raven Press Ltd. 1994); Nagpal and Chandraratna, Current Pharm. Design 2:295-316 (1996), which are both incorporated by reference herein. The retinoid receptors RAR and RXR, like many nuclear receptors, exist as a number of subtypes (RARxcex1, RARxcex2, RARxcex3, and RXRxcex1, RXRxcex2, and RXRxcex3). Additionally, each subtype may exist in different soforms.
The present Applicants have surprisingly discovered that administration of an RAR antagonist or RAR inverse agonist results in the arrest of spermatogenesis in male mammals. By xe2x80x9cantagonistxe2x80x9d is meant that an agent is able to bind to the retinoic acid binding site of an RAR, thereby blocking the binding of retinoic acid to, and activation of the RAR. By xe2x80x9cinverse agonistxe2x80x9d is meant an agent able to suppress the el o activity (homo- or heterodimerization and trans-acting transcriptional control of various genes whose regulation is normally responsive to RAR modulation). A compound will normally be an RAR antagonist if it is an inverse agonist, but the converse is not necessarily true.
The spermatogenetic arrest resulting from treatment of a male mammal with an effective amount of an RAR antagonist or inverse agonist is not accompanied by most other symptoms of hypovitaminosis A, such as blindness, abnormal growth or susceptibility to infectious disease. Testosterone levels appear to remain normal; thus the preferred agents do not significantly affect male libido and sexuality.
This, these compositions have applicability as agents for veterinary or therapeutic application as a male contraceptive.
Some examples of structures and methods of making and using preferred RAR antagonists and inverse agonists are provided in U.S. Pat. No. 5,776,699 and U.S. patent application Ser. Nos. 08/998,319, 08/880,823, and 08/840,040 which are all incorporated by reference herein in their entirety.
Many of the following compounds are included in one or more of these applications.
A class of preferred compounds has the structure: 
wherein
X is S, O, NRxe2x80x2 where Rxe2x80x2 is H or alkyl of 1 to 6 carbons, or
X is [C(R1)2]n where R1 is independently H or alkyl of 1 to 6 carbons, and n is an integer between, and including, 0 and 2, and;
R2 is hydrogen, lower alkyl of 1 to 6 carbons, F, Cl, Br, I, CF3, fluoro substituted alkyl of 1 to 6 carbons, OH, SH, alkoxy of 1 to 6 carbons, or alkylthio of 1 to 6 carbons, and;
R3 is hydrogen, lower alkyl of 1 to 6 carbons or F, and;
m is an integer having the value of 0-3, and;
o is an integer having the value of 0-3, and;
Z is
xe2x80x94Cxe2x89xa1Cxe2x80x94,
xe2x80x94Nxe2x95x90Nxe2x80x94,
xe2x80x94Nxe2x95x90CR1xe2x80x94,
xe2x80x94CR1xe2x95x90N,
xe2x80x94(CR1xe2x95x90CR1)nxe2x80x2xe2x80x94 where nxe2x80x2 is an integer having the value 0-5,
xe2x80x94COxe2x80x94NR1xe2x80x94,
xe2x80x94CSxe2x80x94NR1xe2x80x94,
xe2x80x94NR1xe2x80x94CO,
xe2x80x94NR1xe2x80x94CS,
xe2x80x94COOxe2x80x94,
xe2x80x94OCOxe2x80x94;
xe2x80x94CSOxe2x80x94;
xe2x80x94OCSxe2x80x94;
Y is a phenyl or naphthyl group, or heteroaryl selected from a group consisting of pyridyl, thienyl, furyl, pyridazinyl, pyrimidinyl, pyrazinyl, thiazolyl, oxazolyl, imidazolyl and pyrrazolyl, said phenyl and heteroaryl groups being optionally substituted with one or two R2 groups, or
when Z is xe2x80x94(CR1xe2x95x90CR1)nxe2x80x2xe2x80x94 and nxe2x80x2 is 3, 4 or 5 then Y represents a direct valence bond between said (CR2xe2x95x90CR2)nxe2x80x2 group and B;
A is (CH2)q where q is 0-5, lower branched chain alkyl having 3-6 carbons, cycloalkyl having 3-6 carbons, alkenyl having 2-6 carbons and 1 or 2 double bonds, alkynyl having 2-6 carbons and 1 or 2 triple bonds;
B is hydrogen, COOH or a pharmaceutically acceptable salt thereof, COOR8, CONR9R10, xe2x80x94CH2OH, xe2x80x94CH2OR11, CHO, CH(OR12)2, CHOR13O, xe2x80x94COR7, CR7(OR12)2, CR7OR13O, or tri-lower alkylsilyl, where R7 is an alkyl, cycloalkyl or alkenyl group containing 1 to 5 carbons, R8 is an alkyl group of 1 to 10 carbons or trimethylsilylallyl where the alkyl group has 1 to 10 carbons, or a cycloalkyl group of 5 to 10 carbons, or R8 is phenyl or lower alkylphenyl, R9 and R10 independently are hydrogen, an alkyl group of 1 to 10 carbons, or a cycloalkyl group of 5-10 carbons, or phenyl or lower alkylphenyl, R11 is lower alkyl, phenyl or lower alkylphenyl, R12 is lower alkyl, and R13 is divalent alkyl radical of 2-5 carbons, and
R14 is (R15)r-phenyl, (R15)r-naphthyl, or (R15)r-heteroaryl where the heteroaryl group has 1 to 3 heteroatoms selected from the group consisting of O, S and N, r is an integer having the values of 0-5, and
R15 is independently H, F, Cl, Br, I, NO2, N(R8)2, N(R8)COR8, NR8CON(R8)2, OH, OCOR8, OR8, CN, an alkyl group having 1 to 10 carbons, fluoro substituted alkyl group having 1 to 10 carbons, an alkenyl group having 1 to 10 carbons and 1 to 3 double bonds, alkynyl group having 1 to 10 carbons and 1 to 3 triple bonds, or a trialkylsilyl or trialkylsilyloxy group where the alkyl groups independently have 1 to 6 carbons.
Another preferred class of compounds has the structure: 
wherein
X is S, O, NRxe2x80x2 where Rxe2x80x2 is H or alkyl of 1 to 6 carbons, or
X is [C(R1)2]n where R1 is independently H or alkyl of 1 to 6 carbons, and n is an integer between, and including, 0 and 2, and;
R2 is hydrogen, lower alkyl of 1 to 6 carbons, F, Cl, Br, I, CF3, fluoro substituted alkyl of 1 to 6 carbons, OH, SH, alkoxy of 1 to 6 carbons, or alkylthio of 1 to 6 carbons, and;
R3 is hydrogen, lower alkyl of 1 to 6 carbons or F, and;
m is an integer having the value of 0, 1, 2, or 3, and;
o is an integer having the value of 0, 1, 2, or 3, and;
Y is a phenyl or naphthyl group, or heteroaryl selected from a group consisting of pyridyl, thienyl, furyl, pyridazinyl, pyrimidinyl, pyrazinyl, thiazolyl, oxazolyl, imidazolyl and pyrrazolyl, said phenyl and heteroaryl groups being optionally substituted with one or two R2 groups, and;
A is (CH2)q where q is 0-5, lower branched chain alkyl having 3-6 carbons, cycloalkyl having 3-6 carbons, alkenyl having 2-6 carbons and 1 or 2 double bonds, alkynyl having 2-6 carbons and 1 or 2 triple bonds, and;
B is hydrogen, COOH or a pharmaceutically acceptable salt thereof, COOR8, CONR9R10, xe2x80x94CH2OH, CH2OR11, CH2OCOR11, CHO, CH(OR12)2, CHOR13O, xe2x80x94COR7, CR7(OR12)2, CR7OR13O, or tri4ower alkylsilyl, where R7is an alkyl, cycloalkyl or alkenyl group containing 1 to 5 carbons, R8 is an alkyl group of 1 to 10 carbons or trimethylsilylalkyl where the alkyl group has 1 to 10 carbons, or a cycloalkyl group of 5 to 10 carbons, or R8 is phenyl or lower alkylphenyl, R9 and R10 independently are hydrogen, an alkyl group of 1 to 10 carbons, or a cycloalkyl group of 5-10 carbons, or phenyl or lower alkylphenyl, R11 is lower alkyl, phenyl or lower alkylphenyl, R12 is lower alkyl, and R13 is divalent alkyl radical of 2-5 carbons, and;
R14 is (R15)r-phenyl, (R15)r-naphthyl, or (R15)r-heteroaryl where the heteroaryl group has 1 to 3 heteroatoms selected from the group consisting of O, S and N, r is an integer having the values of 0,1, 2, 3, 4 or 5, and;
R15 is independently H, F, Cl, Br, I, NO2, N(R8)2, N(R8)COR8, NR8CON(R8)2, OH, OCOR8, OR8, CN, an alkyl group having 1 to 10 carbons, fluoro substituted alkyl group having 1 to 10 carbons, an alkenyl group having 1 to 10 carbons and 1 to 3 double bonds, alkynyl group having 1 to 10 carbons and 1 to 3 triple bonds, or a trialkylsilyl or trialkylsilyloxy group where the alkyl groups independently have 1 to 6 carbons, and;
R16 is H, lower alkyl of 1 to 6 carbons, and;
R17 is H, lower alkyl of 1 to 6 carbons, OH or OCOR11, and;
p is 0 or 1, with the proviso that when p is 1 then there is no R17 substituent group, and m is an integer between, and including, 0 and 2.
A further preferred class of compounds is the class of the structure: 
where
X is C(R1)2 or O, and;
R1 is H or alkyl of 1 to 6 carbons, and;
R2 is lower alkyl of 1 to 6 carbons, F, Cl, Br, I, CF3, fluoro substituted alkyl of 1 to 6 carbons, OH, SH, alkoxy of 1 to 6 carbons, or alkylthio of 1 to 6 carbons, and;
m is an integer having the value of 0-3, and;
R3 is lower alkyl of 1 to 6 carbons of F, and;
o is an integer having the value of 0-3, and;
s is an integer having the value of 1-3, and;
R8 is an alkyl group of 1 to 10 carbons or trimethylsilylalkyl where the alkyl group has 1 to 10 carbons, or a cycloalkyl group of 5 to 10 carbons, or R8 is phenyl or lower alkylphenyl, and;
R15 is independently H, F, Cl, Br, I, NO2, N(R8)2, COR8, NR8CON(R8)2, OCOR8, OR8, CN, an alkyl group having 1 to 10 carbons, fluoro substituted alkyl group having 1 to 10 carbons, an alkenyl group having 1 to 10 carbons and 1 to 3 double bonds, an alkynyl group having 1 to 10 carbons and 1 to 3 triple bonds, or a trialkylsilyl or trialkylsilyloxy group where the alkyl groups independently have 1 to 6 carbons, and;
t is an integer having the values of 0, 1, 2, 3, 4, or 5, and;
the CONH group is in the 6 or 7 position of the benzopyran, and in the 2 or 3 position of the dihydronaphthaline ring, or a pharmaceutically acceptable salt of said compound.
Another preferred class of compounds is that of the structure: 
where
X is C(CH3)2 or O, and;
R2 is H or Br, and;
R2xe2x80x2 and R2xe2x80x3 independently are H or F, and;
R3 is H or CH3, and;
R8 H, lower alkyl of 1 to 6 carbons, or a pharmaceutically salt of said compound.
A further class of such compounds has the structure: 
where
X1 is S or O;
X2is CH or N;
R2 is H, F, CF3 or alkoxy of 1 to 6 carbons;
R2*H, F, or CF3;
R8 is H, or lower alkyl of 1 to 6 carbons;
R14 is unsubstituted phenyl, thienyl or pyridyl, or phenyl, thienyl or pyridyl substituted with one to three R15 groups, where R15 is lower alkyl of 1 to 6 carbons, chlorine, CF3, or alkoxy of 1 to 6 carbons, or a pharmaceutically acceptable salt of said compound.
In yet another preferred embodiment of the invention, the compound has the structure: 
wherein
X2 is CH or N, and;
R2 is H, F, or OCH3, and;
R2*H or F, and;
R8 is H, or lower alkyl of 1 to 6 carbons, and;
R14 is selected from the group consisting of phenyl, 4-(lower-alkyl)phenyl, 5-(lower alkyl)-2-thienyl, and 6-(lower alkyl)-3-pyridyl where lower alkyl has 1 to 6 carbons, or a pharmaceutically acceptable salt of said compound.
A further preferred class of such compounds has the structure: 
where
X1 is S or O;
X2 is CH or N;
R2 is H, F, CF3 or alkoxy of 1 to 6 carbons;
R2*H, f, or CF3;
R8 is H, or lower alkyl of 1 to 6 carbons;
R14 is unsubstituted phenyl, thienyl or pyridyl, or phenyl, thienyl or pyridyl substituted with one to three R15 groups, where R15 is lower alkyl of 1 to 6 carbons, chlorine, CF3, or alkoxy of 1 to 6 carbons, or a pharmaceutically acceptable salt of said compound.
In an event more preferred embodiment of the invention, the compound has the structure: 
where
X2 is CH or N, and;
R2 is H, F, or OCH3, and;
R2*H or F, and;
R8 is H, or lower alkyl of 1 to 6 carbons, and;
R14 is selected from the group consisting of phenyl, 4-(lower-alkyl)phenyl, 5-(lower alkyl)-2-thienyl, and 6-(lower alkyl)-3-pyridyl where lower alkyl has 1 to 6 carbons, or a pharmaceutically acceptable salt of said compound.
Another class of compounds for use in a preferred embodiment of the present invention has the following structure: 
where
R2* is H or F;
R8 is H, or lower alkyl of 1 to 6 carbons, and
R14 is selected from the group consisting of phenyl, and 4-(lower-alkyl)phenyl, where lower alkyl has 1 to 6 carbons, or a pharmaceutically acceptable salt of said compound.
Another preferred compound class has the following structure: 
where R8 is H, lower alkyl of 1 to 6 carbons, or a pharmaceutically acceptable salt of said compound.
Yet another preferred compound is one having the following structure: 
where R8 is H, lower alkyl of 1 to 6 carbons, or a pharmaceutically acceptable salt of said compound. When R8 is H, this compound is termed AGN 193109.
Yet another class of compounds contemplated for use in the present invention is that having the structure: 
wherein
X1 is: xe2x80x94C(R1)2xe2x80x94, xe2x80x94C(R1)2xe2x80x94C(R1)2xe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94NR1xe2x80x94, xe2x80x94C(R1)2xe2x80x94Oxe2x80x94, xe2x80x94C(R1)2xe2x80x94Sxe2x80x94, or C(R1)2xe2x80x94NR1xe2x80x94; and
R1 is independently H or alkyl of 1 to 6 carbons; and
R2 is optional and is defined as lower alkyl of 1 to 6 carbons, F, Cl, Br, I, CF3, fluoro substituted alkyl of 1 to 6 carbons, OH SH, alkoxy of 1 to 6 carbons, or alklthio of 1 to 6 carbons; and
m is an integer between, and including, 0 and 4; and
n is an integer between, and including, 0 and 2; and
o is an integer between, and including, 0 and 3; and
R3 is H, lower alkyl of 1 to 6 carbons, F, Cl, Br or I; and
R4 is (R5)p-phenyl, (R5)p-naphthyl, (R5)p-heteroaryl where the heteroaryl group is five-membered or 6-membered and has 1 to 3 heteroatoms selected from the group consisting of O, S, and N; and
p is an integer between, and including, 0 and 5; and
R5 is optional and is defined as independently F, Cl, Br, I, NO2, N(R8)2, N(R8)COR8, N(R8)CON(R8)2, OH, OCOR8, OR8, CN, COOH, COOR8, an alkyl group having from 1 to 10 carbons, an alkenyl group having from 1 to 10 carbons and 1 to three double bonds, alkynyl group having from 1 to 10 carbons and 1 to 3 triple bonds, or a (trialkyl)silyl or (trialkyl)silyloxy group where the alkyl groups independently have from 1 to 6 carbons; and
Y is a phenyl or naphthyl group, or a heteroaryl selected from the group consisting of pyridyl, thienyl, furyl, pyridazinyl, pyrimidinyl, pyrazinyl, thiazolyl, oxazolyl, imidazolyl and pyrrazolyl, said phenyl and heteroaryl groups being optionally substituted with one or two R2 groups, or Y is xe2x80x94(CR3xe2x95x90CR3)rxe2x80x94; and
r is an integer between, and including, 1 and 3; and
A is (CH2)q where q is an integer from 0-5, lower branched chain alkyl having from 3 to 6 carbons, cycloalkyl having from 3 to 6 carbons, alkenyl having from 2 to 6 carbons and 1 or 2 double bonds, alkenyl having from 2 to 6 carbons and 1 or 2 triple bonds, with the proviso that when Y is xe2x80x94(CR3xe2x95x90CR3)rxe2x80x94 then A is (CH2)q and q is 0; and
B is H, COOH or a pharmaceutically acceptable salt thereof, COOR8, CONR9R10, xe2x80x94CH2OH, CH2OR11, CHO, CH(OR12)2, CHOR13O, xe2x80x94COR7, CR7(OR12)2, CR7OR13O, or Si(C1-6alkyl)3, wherein R7 is an alkyl, cycloaLkyl or alkenyl group containing 1 to 5 carbons, R8 is an alkyl group of 1 to 10 carbons or (trimethylsilyl)alkyl, where the alkyl groups has 1 to 10 carbons, or a cycloalkyl group of 5 to 10 carbons, or R8 is phenyl or lower alkylphenyl, R9 and R10 independently are H, a lower alkyl group of 1 to 10 carbons, or a cycloalkyl group of 5-10 carbons, or phenyl or lower alkylphenyl, R11 is lower alkyl, phenyl or lower alkylphenyl, R12 is lower alkyl, and R13 is a divalent alkyl radical of 2-5 carbons. A non-exclusive list of compounds falling within this description, and methods for making this class of compounds are disclosed in U.S. Pat. No. 5,728,846 to Vuligonda et al., the disclosure of which is hereby incorporated by reference as part of this application.
Also useful in the present invention are compounds of the formula:
Y3(R4)xe2x80x94Xxe2x80x94Y1(R1R2)xe2x80x94Zxe2x80x94Y2(R2)xe2x80x94Axe2x80x94B
Where
Y1 is phenyl, naphthyl, or heteroaryl selected from the group consisting of pyridyl, thienyl, furyl, pyridazinyl, pyrimidinyl, pyrazinyl, thiazonyl, ozazolyl, imidazolyl, and pyrrazolyl, said phenyl, naphthyl, and heteroaryl groups being substituted with an R1 group, and further substituted or unsubstituted with one or two R2 groups;
R1 is C1-10 alkyl, 1-ademantyl, 2-tetrahydropyranoxy, trialkylsilanyloxy where alkyl has up to 6 carbons, OH, alkoxy where the alkyl group has up to 10 carbons, alkylthio where the alkyl group has up to 10 carbons, or OCH2OC1-6 alkyl;
R2 is lower alkyl of 1 to 6 carbons, F, Cl, Br, I, CF3, CF2CF3, OH, OR3, NO2, N(R3)2, CN, N3, COR3, NHCOR3, COOH, or COOR3;
X is (C(R3)2, S, SO, SO2, O or NR3;
Z is
xe2x80x94Cxe2x89xa1Cxe2x80x94,
xe2x80x94Nxe2x95x90Nxe2x80x94,
xe2x80x94N(O)xe2x95x90Nxe2x80x94,
xe2x80x94Nxe2x95x90N(O)xe2x80x94,
xe2x80x94Nxe2x95x90CR3xe2x80x94,
xe2x80x94CR3xe2x95x90N,
xe2x80x94(CR3xe2x95x90CR3)nxe2x80x94 where n is an integer having the value 0-5,
xe2x80x94COxe2x80x94NR3xe2x80x94,
xe2x80x94CSxe2x80x94NR3xe2x80x94,
xe2x80x94NR3xe2x80x94CO,
xe2x80x94NR3xe2x80x94CS,
xe2x80x94COOxe2x80x94,
xe2x80x94OCOxe2x80x94;
xe2x80x94CSOxe2x80x94;
xe2x80x94OCSxe2x80x94; or
xe2x80x94COxe2x80x94CR3xe2x95x90R3xe2x80x94O,
R3 is independently H or lower alkyl of 1 to 6 carbons;
Y2 is a phenyl or naphthyl group, or heteroaryl selected from a group consisting of pyridyl, thienyl, furyl, pyridazinyl, pyrimidinyl, pyrazinyl, thiazolyl, oxazolyl, imidazolyl and pyrrazolyl, said phenyl, naphthyl and heteroaryl groups being unsubstituted or substituted with one or two R2 groups, or
when Z is xe2x80x94(C3xe2x95x90CR3)nxe2x80x94 and n is 3, 4 or 5 then Y2 represents a direct valence bond between said xe2x80x94(CF3xe2x95x90CR3)n group and B;
Y3 is phenyl, naphthyl, or heteroaryl selected from a group consisting of pyridyl, thienyl, furyl, pyridazinyl, pyrimidinyl, pyrazinyl, thiazolyl, oxazolyl, imidazolyl and pyrrazolyl, said phenyl, naphthyl and heteroaryl groups being unsubstituted or substituted with one to three R4 groups, where R4 is alkyl of 1 to 10 carbons, fluoro-substituted alkyl of 1 to 10 carbons, alkenyl of 2 to 10 carbons and having 1 to 3 triple bonds, F, Cl, Br, I, NO2, CN, NR3, N3, COOH, COOC1-6 alkyl, OH, SH, OC1-6 alkyl, and SC1-6 alkyl;
A is (CH2)q where q is from 0-5, lower branched alkyl having 3-6 carbons, cycloalkyl having 3-6 carbons, alkenyl, having 2-6 carbons and 1-2 double bonds, alkynyl having 2-6 carbons and 1 to 2 triple bonds, and
B is hydrogen, COOH or a pharmaceutically acceptable salt thereof, COOR8, CONR9R10, xe2x80x94CH2OH, CH2OR11, CH2OCOR11, CHO, CH(OR12)2, CHOR13O, xe2x80x94COR7, CR7(OR12)2, CR7OR13O, or Si(C1-6alkyl)3, where R7 is an alkyl, cycloalkyl or alkenyl group containing 1 to 5 carbons, R8 is an alkyl group of 1 to 10 carbons or trimethylsilylalkyl where the alkyl group has 1 to 10 carbons, or a cycloalkyl group of 5 to 10 carbons, or R8 is phenyl or lower alkylphenyl, R9 and R10 independently are hydrogen, an alkyl group of 1 to 10 carbons, or a cycloalkyl group of 5-10 carbons, or phenyl or lower alkylphenyl, R11 is lower alkyl, phenyl or lower alkylphenyl, R12 is lower alkyl, and R13 is divalent alkyl radical of 2-5 carbons, or a pharmaceutically acceptable salt of said compound. These compounds are disclosed in U.S. patent application Ser. No. 08/840,040, to Song et al., which application shares common ownership with the present application and is incorporated by reference herein in its entirety.
Additional RAR antagonists or inverse agonists are described in U.S. patent application Ser. No. 08/845,019, to Song and Chandraratna, which is incorporated by reference herein in its entirety; this application shares common ownership with the present application. Also, compounds useful in the methods of the present invention are disclosed in International Application Publication No. WO 94/14777, to Yoshimura et al., which is also incorporated by reference herein in its entirety. This latter application discloses RAR antagonists. A non-exclusive list of the structures of some preferred compounds disclosed therein can be found in FIG. 1 hereof.
Furthermore, the structures of additional compounds useful in the present invention are disclosed below.
A. 
where n is an integer from 1 to 10.
B. 
where n is an integer from 1 to 10.
C. 
D. 
E. 
A particularly preferred subgroup of RAR antagonists or inverse agonists is the set of those RAR antagonists or inverse agonists that lack antagonist or inverse agonist activity at one or more subclass of RARs, such as the RARxcex1, RARxcex2, or RARxcex3 receptors; such xe2x80x9csubclass-specificxe2x80x9d activity may result in the minimization of toxicity of the drug. Such compounds may have activity only at the RARxcex1, RARxcex2, or RARxcex3 receptors, or at any combination of these (other than at all of them). Determination of whether a compound has subclass-specific specific inverse agonist activity is done through translational screening as disclosed in U.S. patent application Ser. No. 09/042,943, to Klein et al., and Ser. No. 09/108,298, to Nagpal et al., both of which are incorporated by reference herein in their entirety.
The compounds disclosed herein clearly suggest the synthesis and use of other compounds structurally similar to these, for use in the methods of the present invention. In addition to the compounds referred to herein, other agents that have RAR antagonist and/or inverse agonist activity are also anticipated to arrest spermatogenesis in mammals and thus be useful as male contraceptive agents in the invention of the present application.
The effective agents of the present invention may be provided orally, as in a liquid, syrup, suspension, tablet, capsule, gelatin-coated formulation or the like. Additionally, the contraceptive agents of the present invention have been demonstrated to be effective when applied topically. Topical delivery means include creams, gels, lotions, emulsions, suspensions, skin patches and the like. Additional delivery means may include inhalants, suppositories, and nasal sprays. Time-release formulations may be made for either oral or topical delivery.
For therapeutic applications in accordance with the present invention the antagonist compounds are incorporated into pharmaceutical compositions, such as tablets, pills, capsules, solutions, suspensions, creams, ointments, gels, salves, lotions and the like, using such pharmaceutically acceptable excipients and vehicles which per se are well known in the art. For example, preparation of topical formulations are well described in Remington""s Pharmaceutical Science, Edition 17, Mack Publishing Company, Easton, Pa.; incorporated by reference herein. For topical application, the RAR antagonist or inverse agonist compounds could also be administered as a powder or spray, particularly in aerosol form. If the drug is to be administered systemically, it may be prepared as a powder, pill, tablet or the like or as a syrup or elixir suitable for oral administration. For intravenous or intraperitoneal administration, the drug compound will be prepared as a solution or suspension capable of being administered by injection. In certain cases, it may be useful to formulate the antagonist compounds by injection. In certain cases, it may be useful to formulate the antagonist compounds in suppository form or as extended release formulation for deposit under the skin or intramuscular injection.
The antagonist or inverse agonist compounds will be administered in a therapeutically effective dose in accordance with the invention. A therapeutic concentration will be that concentration which is effective to cause diminution or cessation of spermatogenesis in the testes of the male mammal. It is currently thought that a formulation containing between about 0.5 and about 0.001 mg/kg of body weight, more preferably between about 0.3 mg/kg and 0.005 mg/kg, even more preferably about 0.075 mg/kg of body weight and about 0.01 mg/kg of body weight will constitute a therapeutically effective concentration for oral application, with routine experimentation providing adjustments to these concentrations for other routes of administration if necessary.
Accordingly, in one embodiment the present invention comprises a method of inhibiting spermatogenesis in a mammal comprising the administration of an effective amount of an RAR antagonist or RAR inverse agonist at time intervals sufficient to inhibit or arrest spermatogenesis. In a further embodiment, the mammal is a human.
In a further preferred embodiment, the RAR antagonist or RAR inverse agonist is administered orally through the use of a liquid, syrup, suspension, tablet, capsule, or gelatin-coated formulation. In another preferred embodiment, the RAR antagonist or RAR inverse agonist is topically administered, through the use of means including a patch, cream, lotion, emulsion, or gel. In yet another embodiment, the RAR antagonist or RAR inverse agonist is formulated in an inhalant, suppository or nasal spray.
The present invention concerns compositions and methods for the prophylactic prevention of pregnancy by the inhibition or arrest of spermatogenesis in male mammals. Spermatogenesis occurs in the seminiferous tubules of the testes of sexually mature male mammals. These tubules consist of a basement membrane surrounding an intra-tubule lumen. Specialized columnar cells termed Sertoli cells lie against the basement membrane and protrude into the lumen; the germ cells remain closely associated with the Sertoli cells throughout spermatogenesis.
Spermatogonia, male gamete stem cells, lie between the Sertoli cells and the basement membrane. Mitosis of a spermatogonium gives rise to two daughter cells; one may remain near the basement membrane as a spermatogonium and the other may develop, through subsequent rounds of mitosis, into a primary spermatocyte. As it develops the cells that become diploid primary spermatocytes are crowded closer to the tubule lumen.
The primary spermatocyte then enters meiosis and gives rise to haploid spermatids. These spermatids remain closely associated with the Sertoli cell, now at a location close to the lumen, and undergo a metamorphosis mediated partly by the Sertoli cell, maturing into spermatozoa. These cells are then released into the lumen of the seminiferous tubule.
The seminiferous tubules are closely packed together in the testes, being separated by connective tissue containing fibrocytes and vessels. An inhabitant of the spaces between the tubules is a steroidogenic somatic cell termed the Leydig cell. These cells synthesize the steroid hormone testosterone, which is an important stimulus for the differentiation of germ cells; the hormone diffuses into the seminiferous tubules where it stimulates spermatogenesis.
The time course of complete spermatogenesis is long; approximately 64 days in humans and 54 days in rats. This time course can be divided into 4 stages. In the first stage, spermatocytogenesis, the spermatogonia divide and give rise to primary spermatocytes. In the second stage, the primary spermatocytes undergo meosis and give rise to spermatids. In the third stage, spermoigenesis, the spermatids metamorphize into spermatozoa. In the final stage, maturation, the spermatozoa mature and are released into the seminiferous tubule. The spermatozoa undergo final maturation in the epiphysis. Cells in each of these four stages can be seen as xe2x80x9clayersxe2x80x9d in normal seminiferous tubules, with the least mature cells nearer the basement membrane, and the most mature cells near the lumen. The absence of cells of one or more stage is indicative of an event blocking or arresting a stage in spermatogenesis.
Although the exact mechanism underlying hormonal and gene regulation occurring in spermnatogenesis is not precisely known, and the scope of the present invention is not to be limited by theory, it is believed that testosterone production is regulated by the pituitary hormone, luteinizing hormone (LH). Another pituitary hormone, follicle-stimulating hormone (FSH), is also involved in the regulation of spermatogenesis, with primary hormone receptors being present on-the Sertoli cells. One effect of FSH on Sertoli cells is to stimulate the production of androgen-binding protein (ABP), which has a high binding affinity for testosterone and helps retain the steroid within the seminiferous tubules and sustain its effect on spermatogenesis.
Another peptide, termed inhibin, is thought to be secreted by Sertoli cells in response to the binding of FSH. Inhibin, in turn, appears to act on target cells within the pituitary to inhibit FSH secretion. Thus, inhibin may operate to act as a negative feedback regulator for the release of FSH and thus the production of ABP, with one consequence being the prevention of overstimulation by testosterone. Overproduction of inhibin could serve to lower the concentration of testosterone within the seminiferous tubules.
Thus, the regulation of spermatogenesis appears to include the regulation of gene expression and synthesis of a number of factors that either act as peptide hormones themselves or are involved in the sequestration or regulation of hormones important in spermatogenesis. Retinoid nuclear receptors (retinoic acid receptors (RAR) and retinoid X receptors (RXR)) are known to be involved in the ligand-mediated transcriptional regulation of various genes, which may include some of these factors.